Microfluidic devices are used to control and manipulate very small volumes of fluids, often on the order of microliter or nanoliter volumes. Sometimes also referred to as a microfluidic device or a Lab-on-a-Chip, microfluidic devices are particularly useful in applications that employ rare or expensive fluids, such as proteomics and genomics. The small size of the microfluidic device allows for the analysis of minute quantities of a sample.
Some microfluidic devices are used for sample analysis by utilizing techniques such as chromatography to cause chromatographic separation of molecules within the sample. High-performance liquid chromatography (HPLC, sometimes also referred to as high-pressure liquid chromatography), involves pumping a liquid (the mobile phase) at high pressure through the separation column. Chromatographic separation occurs when the mobile phase carries molecules in the sample through the stationary phase where the molecules interact with the stationary phase surface. Different molecules interact differently with the stationary phase, resulting in the molecules having a different velocity through the separation column. This results in a separation of the molecules as they pass through the separation column. An enrichment column can also be used to enrich molecules in the sample before passing the sample through the separation column.
A difficulty can arise when a sample, such as a complex biological sample is dissolved in an organic solvent, because the organic solvent may not be compatible with the enrichment and/or separation column. In addition, the organic solvent can interfere and elute or partially elute the sample from the enrichment column and/or separation column before separation has occurred. Thus, there remains a need to develop methods and devices for resolution and separation of samples, such as complex biological samples.